1. Field of the Invention
The present invention relates to a semiconductor integrated circuit (contact structure) and a manufacturing method thereof and, in particular, to a wire of a borderless structure.
2. Description of the Background Art
In recent years, a wire of a borderless structure has been employed along with the refinement of semiconductor integrated circuits. Hereinafter, aluminum alloys containing about 0.5% of aluminum or copper are referred to as "aluminum." In a borderless structure, a wire formed on an interlayer insulation film having a wire burying hole, is in contact with a conductor in the hole, with part of the hole not covered.
A method of manufacturing wires of conventional borderless structures is described by referring to FIGS. 52 and 53. In the structure shown in FIG. 52, an underlying wire layer 920, an interlayer insulation film 930 having a wire burying hole 931, a barrier metal layer 941, a tungsten plug 942, an aluminum wire layer 952, an antirellection layer 953, and a resist 954, are disposed on a base layer 910. The base layer 910 is a semiconductor substrate on which an element and the like are formed, or is an interlayer insulation film formed on a semiconductor substrate. The metal formed above the interlayer insulation film 930 is defined as a wire layer 950, and the metal in the wire burying hole 931 is defined as a conductor 940. The aluminum wire layer 952 is in contact with the tungsten plug 942. By using the resist 954 as a mask, the wire layer 950 is subjected to an etching, resulting in a wire of a borderless structure, as shown in FIG. 53.
The upper portion of the conductor 940, however, comprises the aluminum wire layer 952, and the contact area between the aluminum wire layer 952 and the tungsten plug 942 is exposed by the etching. Furthermore, it was found experimentally that an echant enters the contact area between the aluminum wire layer 952 and the tungsten plug 942 to cause a side etch and leads to the erosion of the aluminum wire layer 952 in this area. A pronounced clearance 970 due to the erosion of the aluminum wire layer 952 may generate a clearance 970 between the conductor 940 and the wire layer 950, causing disconnection of the wire.